Hydrogen production characteristics from dark fermentation of maltose by an isolated strain F.P 01

A hydrogen producing strain F.P 01 was newly isolated from cow dung sludge in an anaerobic bioreactor. The strain F.P 01 was a mesophilic and facultative anaerobic bacterium, which exhibited gram-negative staining in both the exponential and stationary growth phases, and a regular long rod-shaped bacteria with the size of 0.6–0.9 μm × 1.2–2.5 μm, and also could biodegrade a variety of carbohydrates such as glucose, xylose, maltose, etc. The effects of important process parameters on hydrogen producing of F.P 01 were further investigated from hydrogen fermentation of maltose by strain F.P 01, including substrate concentration, medium pH, etc. And the results showed that hydrogen production potential and hydrogen production rate from maltose of this strain F.P 01 was180 mLH₂/g-maltose and 4.0 mLH₂/h, respectively. The corresponding hydrogen concentration of 58–73% was also be observed. Both butyric acid and acetic acid as main by-product was left in the reactor.     

The production of biohydrogen by a novel strain Clostridium sp. YM1 in dark fermentation process

In view of increasing attempts for the production of renewable energy, the production of biohydrogen energy by a new mesophilic bacterium Clostridium sp. YM1 was performed for the first time in the dark fermentation. Experimental results showed that the fermentative hydrogen was successfully produced by Clostridium sp. YM1 with the highest cumulative hydrogen volume of 3821 ml/L with a hydrogen yield of 1.7 mol H₂/mol glucose consumed. Similar results revealed that optimum incubation temperature and pH value of culture medium were 37 °C and 6.5, respectively. The study of hydrogen production from glucose and xylose revealed that this strain was able to generate higher hydrogen from glucose compared to that from xylose. The profile of volatile fatty acids produced showed that hydrogen generation by Clostridium sp. YM1 was butyrate-type fermentation. Moreover, the findings of this study indicated that an increase in head space of fermentation culture positively enhanced hydrogen production.     

Treatment with moderate concentrations of NaHSO3 enhances photobiological H2 production in the cyanobacterium Anabaena sp. strain PCC 7120

In cyanobacteria, treatment with low concentrations of NaHSO₃ can enhance photosynthetic efficiency, whereas NaHSO₃ in high amounts often inhibits cell growth and photosynthesis may even cause death. In the present study, our results showed that treatment with moderate concentrations of NaHSO₃ considerably improved the yield of photobiological H₂ production in the filamentous N₂-fixing cyanobacterium Anabaena sp. strain PCC 7120. Under steady state conditions, the accumulated H₂ levels in cells treated with 1 mM NaHSO₃ were approximately 10 times higher than that in untreated cells. Such improvement occurred in heterocysts and was most likely caused by increases in the expression and activity of nitrogenase. The effects of treatment with low, moderate, and high concentrations of NaHSO₃ in cyanobacteria were proposed on the basis of the results obtained in the present study and from previous knowledge.